The present invention relates to a high speed linear bagging machine and particularly a machine for placing a plastic bag over a sliced loaf of bread.
In particular, the present invention is an improvement of PCT Application WO94/27867 published on Dec. 8, 1994. The packaging equipment as described in that patent was designed for the automatic packaging of sliced bread in loaf form and wherein the apparatus would operate automatically thereby reducing the labor costs associated with the packaging of sliced bread whilst at the same time reducing labor costs and minimizing contact between laborers and the bread loaf being packaged, this latter advantage being very significant. In particular that machine was concerned with the method of holding a sliced loaf of bread in position and pulling an open bag thereover and then releasing the bag to a bag closing station.
Prior to that PCT and as described in U.S. Pat. No. 4,457,124, the machines comprised of delivering loaves of bread to a loading station where a pusher would push the loaf of bread into a bag and then create a vacuum to draw air out of the bag. A sealing device then sealed the bag and the pusher releases the bag so that a conveyor could carry the bag away from the machine. It is pointed out that all of this known prior art machinery utilized complicated drives and mechanical cams and gears to time and position the components used to bag the bread in a non-stationary scoop type bread bagger. These designs required frequent mechanical adjustments to the infeed conveyor flights to accommodate different loaf sizes and the scoop position/timing could not be optimized for different loaf sizes. The basic machine cycle was fixed relative to its position in time by mechanical pneumatic devices and fixed ratio drives were utilized. Furthermore, the infeed conveyor and the discharge conveyor were provided with separate drives and because of their mechanical mechanisms frequent adjustments were necessary to try to synchronize their drives and it became more difficult to then synchronize the associated reciprocating bagger device which either pushed the loaf into the bag or drew the bag over the loaf.
Another disadvantage of prior art machines is that because of their complex drive and mechanical structures, the machines were subjected to vibrations which destabilized the bag engaging mechanism and this made it difficult for the bag engaging elements to consistently engage a bag and draw it over the loaf as this mechanism required high precision. This caused machine malfunctions and frequent stoppages thereby requiring constant supervision, which is not the intent of such apparatus. In an attempt to circumvent this problem, additional bracing of the frame was necessary and this resulted in machines which were fairly large and not compatible with other machines.
Another drawback of prior art machines is that they are not versatile to adapt to various types of bag formers or bag storing wicket assemblies which often cannot be located at a precise location required by the bag engaging device. Accordingly, there was a restriction on the type of bag supplying equipment that could be used with different types of bagging machines.
A still further disadvantage of the prior art equipment is that they cannot operate accurately at high speed. High speed, with respect to bagging a sliced bread is defined as a handling rate of one bag per second or slightly better. Because the three stations associated with prior art machines are independently operated, this makes it very difficult to obtain precision and machine stability at these high bagging rates of between 60 to 80 loaves per minute.
It is a feature of the present invention to provide a high speed linear bagging machine and method of operation which substantially overcomes the above-mentioned disadvantages of the prior art.
Another feature of the present invention is to provide a high speed linear bagging machine and method of operation which is adjustable and programmable to handle bread loaves of different sizes and bags also of different sizes and wherein the infeed conveyor, the discharge conveyor and the reciprocating high speed linear bagger are all synchronized to one another.
Another feature of the present invention is to provide a high speed linear bagging machine which has a lower center of gravity than the prior art machines and wherein the machine is compatible with other associated machines such as bag formers and bag closing machines and wherein the problem of vibration is substantially reduced thereby making the machine very reliable and substantially free of the above-mentioned malfunctions of prior art machines thereby greatly reducing the cost of operation.
Another feature of the present invention is to provide a high speed linear bagging machine which is provided with an automated control system providing for the preprogramming of machine parameters.
Another feature of the present invention is to provide a high speed linear bagging machine wherein the reciprocating linear bagger is provided with an adjustable stroke length to adapt the machine with various bag forming equipment or bag delivery equipment.
Another feature of the present invention is to provide a high speed linear bagging machine having a reciprocating linear bagger and wherein at least one of the scoops of the bagger is displaceable to positively engage the bag and stretch it with a predetermined pressure and to draw it over the sliced loaf while maintaining the sliced loaf in a stable condition.
Another feature of the present invention is to provide a high speed linear bagging machine wherein the infeed and discharge conveyors are synchronized through a common drive and wherein the bread conveying elements may be adjusted to adapt to bread loaves of different sizes to synchronize same with the reciprocating linear bagger.
According to the above features, from a broad aspect, the present invention provides a high speed linear bagging machine which comprises a product carrying infeed conveyor for transporting a product to be bagged to a bagging station. A discharge conveyor is provided adjacent the bagging station for transporting a bagged product. A reciprocating linear bagger assembly having a straight stator slide and a carriage connected to a pair of coils is displaceable along the stator slide. Stroke control means is further provided for controlling the coils and dependent on a desired forward and rearward displacement stroke of the carriage along the slide. A product receptacle is secured to the carriage and displaceable to the bagging station. Bag engaging means is connected to the carriage. Product arresting means is displaceable for abutting relationship with the product at the bagging station. The bag engaging means engages an open end of a bag at a forward end of the displacement stroke adjacent the bagging station and withdraws the open end of the bag over the product which is maintained substantially stationary by the product arresting means during the reverse stroke of the carriage whereby to insert the product in the bag and discharge the bagged product from the product receptacle. Detection means is associated with the infeed conveyor and the control means to detect the position of the product. The infeed and discharge conveyors have a common synchronized drive feeding a speed indicator signal to the control means to synch the reciprocating linear bagger with the conveyors.
According to a still further broad aspect of the present invention there is provided a method of bagging a product comprising the steps of transporting a product to be bagged on an infeed conveyor to a bagging station. The product is detected and a control means is fed a signal to indicate the position of the product prior to the product reaching the bagging station. A reciprocating linear bagger is displaced along a straight stator slide through a predetermined forward stroke to position a product receptacle at the bagging station to receive the product thereon and to simultaneously engage an open end of a bag at a bag dispensing station by a pair of arm elements. The open end of the bag is tensioned by applying regulated pressure to an articulated one of the arm elements. A product arresting means is disposed in abutting relationship with a first end of the product discharged on the product receptacle and disposed axially opposite to the engaged bag open end. The reciprocating linear bagger is then displaced through a predetermined rearward stroke to draw the open end of the engaged bag over the product from an opposed end of the product. The bag product is then discharged on a discharge conveyor and the product arresting means is withdrawn from its arresting position with the product.